Concrete Calculator
Calculate how much concrete you need for a slab, including cubic yards, cubic feet and estimated cost.
About the Concrete Calculator
This calculator estimates the volume of concrete needed to pour a rectangular slab, such as a patio, sidewalk or shed pad. It converts your slab dimensions into cubic feet and cubic yards — the units concrete is typically ordered in — and also estimates how many pre-mixed 80 lb bags you'd need if you're mixing by hand instead of ordering ready-mix.
Formula: Cubic Feet = Length × Width × (Thickness ÷ 12); Cubic Yards = Cubic Feet ÷ 27; Bags = Cubic Feet ÷ 0.6 (an 80 lb bag yields about 0.6 cubic feet of concrete)
Ready-mix concrete is sold by the cubic yard, so always round up to the nearest quarter yard when ordering, and add 5-10% extra to account for spillage, uneven subgrade and form loss.